scsi: ufs-qcom: Add reset control support for host controller

Add reset control for host controller so that host controller can be reset
as required in its power up sequence.

Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Avri Altman <[e-mail]>
Signed-off-by: Can Guo <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/ufs/ufs-qcom.c

···
 	mb();
 }
 
+/**
+ * ufs_qcom_host_reset - reset host controller and PHY
+ */
+static int ufs_qcom_host_reset(struct ufs_hba *hba)
+{
+	int ret = 0;
+	struct ufs_qcom_host *host = ufshcd_get_variant(hba);
+
+	if (!host->core_reset) {
+		dev_warn(hba->dev, "%s: reset control not set\n", __func__);
+		goto out;
+	}
+
+	ret = reset_control_assert(host->core_reset);
+	if (ret) {
+		dev_err(hba->dev, "%s: core_reset assert failed, err = %d\n",
+				 __func__, ret);
+		goto out;
+	}
+
+	/*
+	 * The hardware requirement for delay between assert/deassert
+	 * is at least 3-4 sleep clock (32.7KHz) cycles, which comes to
+	 * ~125us (4/32768). To be on the safe side add 200us delay.
+	 */
+	usleep_range(200, 210);
+
+	ret = reset_control_deassert(host->core_reset);
+	if (ret)
+		dev_err(hba->dev, "%s: core_reset deassert failed, err = %d\n",
+				 __func__, ret);
+
+	usleep_range(1000, 1100);
+
+out:
+	return ret;
+}
+
 static int ufs_qcom_power_up_sequence(struct ufs_hba *hba)
 {
 	struct ufs_qcom_host *host = ufshcd_get_variant(hba);
···
 	int ret = 0;
 	bool is_rate_B = (UFS_QCOM_LIMIT_HS_RATE == PA_HS_MODE_B)
 							? true : false;
+
+	/* Reset UFS Host Controller and PHY */
+	ret = ufs_qcom_host_reset(hba);
+	if (ret)
+		dev_warn(hba->dev, "%s: host reset returned %d\n",
+				  __func__, ret);
 
 	if (is_rate_B)
 		phy_set_mode(phy, PHY_MODE_UFS_HS_B);
···
 	/* Make a two way bind between the qcom host and the hba */
 	host->hba = hba;
 	ufshcd_set_variant(hba, host);
+
+	/* Setup the reset control of HCI */
+	host->core_reset = devm_reset_control_get(hba->dev, "rst");
+	if (IS_ERR(host->core_reset)) {
+		err = PTR_ERR(host->core_reset);
+		dev_warn(dev, "Failed to get reset control %d\n", err);
+		host->core_reset = NULL;
+		err = 0;
+	}
 
 	/* Fire up the reset controller. Failure here is non-fatal. */
 	host->rcdev.of_node = dev->of_node;

drivers/scsi/ufs/ufs-qcom.h

···
 #define UFS_QCOM_H_
 
 #include <linux/reset-controller.h>
+#include <linux/reset.h>
 
 #define MAX_UFS_QCOM_HOSTS	1
 #define MAX_U32                 (~(u32)0)
···
 	u32 dbg_print_en;
 	struct ufs_qcom_testbus testbus;
 
+	/* Reset control of HCI */
+	struct reset_control *core_reset;
 	struct reset_controller_dev rcdev;
 
 	struct gpio_desc *device_reset;